Study of..... chemical reactions 2 🎷

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What is a chemical reaction?

 A reaction in which a change in reactant or reactants produces a substance with new properties or substances.

In other words a process in which reactants undergo a change in their chemical properties, resulting in the formation of new substances.

In chemical reactions chemical properties change.

 Chemical changes are irreversible.

 Today we are looking at the types of chemical reactions.

1. Combination Reaction: When two or more reactants combine to form only one product then it is called a combination reaction.

   Ex. Hydrogen reacts with oxygen in the air to form water.

     

2H2 + O2 = 2H2O

 Iron reacts with sulfur to form iron sulphide.

  

 Fe + S = FeS

   

Many of us are familiar with the example of two reactants but many students don't know about 3 reactants.

  

Ex. Carbon dioxide gas is passed through freshly prepared quicklime for long duration then we get calcium bicarbonate a single product.

    

 CaCO3 + H2O + CO2 = Ca(HCO3)2

2. Decomposition Reaction: A reaction in which from only one reactone two or more products form is called a decomposition reaction.

   Ex. Calcium carbonate 

when heated up to 1000* celsius temperature it decomposes into calcium oxide and carbon dioxide. 

    

 CaCO3 = CaO + CO2

3. Displacement Reaction:

When a highly reactive element displaces a less reactive element to form a new product it is called a displacement reaction.

   Ex. Zinc displaces copper from copper sulfate solution.

     

Zn + CuSO4 = ZnSO4 + Cu

4. Double Displacement Reaction: when there is an exchange of ions that take place in between two reactants to form two new products and one of them is precipitated then it is called a double displacement reaction.

In a double displacement reaction two reactants are two metal salts.

   Ex. Barium chloride reacts with sodium sulfate to produce barium sulfate and sodium chloride.

     

BaCl2 + Na2SO4 = BaSO4 + 2NaCl

5. Neutralization Reaction: when acid reacts with base to form salt and water it's called neutralization reaction.

   Ex. Hydrochloric acid reacts with sodium hydroxide to form sodium chloride and water.

    

HCl + NaOH = NaCl + H2O

6. Exothermic Reaction: At the time of chemical reaction when heat is liberated then it is called as exothermic reaction.

   Ex. Sodium reacts with water to produce sodium hydroxide and hydrogen gas.

     

2Na + 2H2O = 2NaOH + H2

In this process too much heat is liberated.

7. Endothermic Reaction: The reaction in which heat is absorbed then it is called an endothermic reaction.

   Ex. Sugar when added in water it absorbs heat.

     

C12H22O11 (s) + H2O (l) = C12H22O11 (aq)

8. Redox Reaction: A reaction in which oxidation and reduction takes place simultaneously then it is called a redox reaction.

   Ex. 

   

 9.  Fast Reaction: The reaction which takes a shorter time to complete is called a fast reaction.

Ex.Sodium reacting with water.

  10 .Slow Reaction: The reaction which takes more time for completion is called a slow reaction.

The reactions between covalent compounds are slow.

 Ex. A) Rusting of iron B) Fermentation process 

        Fe2O3.nH2O

   11. Combustion Reaction: A reaction between fuel and oxygen is called a combustion reaction or burning.

In this reaction

 energy is released in the form of light and heat.

 Hydrogen and oxygen reacting to form water.

 2H2 + O2 = 2H2O

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